According the user guide (https://helpcenter.veeam.com/docs/backup/vsphere/system_requirements.html?ver=95#target
), Veeam 9.5 supports DD OS 5.4 to 6.0:
Dell EMC DataDomain (DD OS version 5.4, 5.5, 5.6, 5.7 or 6.0) with DDBoost license. Both Ethernet and Fibre Channel (FC) connectivity is supported.
But according to the EMC Compatibility Guide (http://compatibilityguide.emc.com:8080/CompGuideApp/getDataDomainBoostCompGuidePage.do
) the Min DD OS for Veeam 9.5 is 5.7.
My DD OS version is 5.5 and my Veeam version is 8, can I upgrade to 9.5?